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Biomedical subjects

K Messmer

Publications and source records attributed to K Messmer.

At least 415 records · Page 23Linked to original sources
PubMed1981

[The effect of PEEP ventilation on hemodynamics and regional blood flow (author's transl)].

The beneficial effects of PEEP on lung function may be counteracted by its hemodynamic sequelae induced by a reduction of venous return due to the elevated intrathoracic pressure, and by an increased right ventricular afterload secondary to the rise of pulmonary vascular resistance. PEEP redistributes cardiac output in favor of brain, heart, adrenals and intestines, whereas the perfusion of stomach, pancreas and thyroid is diminished out of proportion to the fall of cardiac output. Total renal blood flow is relatively little affected; however, redistribution of intrarenal blood flow will result in a marked salt-water-retention. Reduction of hepatic artery flow, at higher levels of PEEP, may jeopardize liver tissue oxygenation. - Under clinical conditions, individual differences regarding preexisting cardiopulmonary and peripheral-vascular diseases may modify the PEEP-induced hemodynamic alterations in a wide range.

Blood Circulation↗
PubMed1981

[Changes in microcirculation by the administration of sodium nitroprusside and nitroglycerin].

The effects of hypotension induced by sodium nitroprusside (SNP) or nitroglycerin (NTG) were evaluated in hamsters (n = 12). No differences in macrohemodynamic parameters were found during and after hypotension with either drug tested. SNP dilated predominantly the precapillaries and NTG dilated all microvascular segments. Blood cell velocity decreased in both groups. A significant volume of blood was diverted through av-shunts during SNP hypotension of 40 mm Hg. Capillary density decreased significantly during and after SNP-induced hypotension, whereas capillary density remained unchanged when NTG was used. The data favour the use of NTG when hypotension is deliberately induced.

Animals↗
PubMed1981

Tissue pO2 and transcutaneous pO2 as guidelines in experimental and clinical drug evaluation.

Tissue pO2 measurements on skeletal muscle surface both in patients and in animals in a model of occlusive disease revealed local tissue hypoxia that, until now, had not been detected with any other method. This kind of local tissue hypoxia is interpreted as a disturbance of local microflow distribution in the presence of unchanged regional blood flow rate. In response to buflomedil infusion, tissue pO2 histograms improved without any change in regional blood flow or distal blood pressure. In comparison to healthy volunteers, transcutaneous pO2 measurements in patients allowed establishment of of tcpO2 profiles along the lower extremity which were in agreement with angiographic localization of vessel occlusion. In a preliminary study, buflomedil infusion (3 mg/kg) over 30 minutes caused a significant increase in tcpO2 in 5 patients in the absence of any significant change of segmental blood pressure. It is concluded that both tissue pO2 and tcpO2 measurements are able to provide unique information about local changes of the microcirculation in occlusive vessel disease.

Animals↗
PubMed1981

Microcirculation of transplanted tumors.

A transparent chamber was implanted in the dorsal skin flap of 32 Syrian gold hamsters, 48 h after microsurgery, 4x10(4) cells of the amelanotic melanoma A-Mel-3 were transplanted s.c. in the area exposed for daily in vivo microscopy (16 animals). A platinum multiwire electrode and quantitative video-techniques were utilized for measurements of local pO2, microvascular morphology and measurements of local PO2, microvascular morphology and capillary hemodynamics. When compared to controls (16 animals), mean local PO2 on the tumor's surface decreased with tumor development. The density of erythrocyte perfused capillaries in the melanoma was elevated 4 days after humor transplantation indicating excessive neovascularization. Probably due to increased intratumor tissue pressure and thrombosis, capillary density decreased significantly until day 12, whereas mean capillary blood cell velocity did not change. Of microhemodynamic significance were huge platelet conglomerates consistently noted in short, dilated capillaries as the melanoma edge. As a result, the capillary filling time (15.7 s for melanoma capillaries, 3.2 s for control preparations) was prolonged suggesting an increase in capillary resistance. These findings might indicate that the efficacy of melanoma treatment is diminished by an enhanced capillary resistance. Intratumor tissue pressure and thrombosis with concomitant widening of intercapillary distances might significantly affect the therapy of melanomas.

Animals↗
PubMed1981

Quantitative analysis of microvascular structure and function in the amelanotic melanoma A-Mel-3.

Blood cell velocity, capillary diameter, and capillary length were determined in the microcirculation of the amelanotic hamster melanoma A-Mel-3 as well as in s.c. tissue of tumor-free animals. Studies were carried out using a dorsal skin flap chamber, intravital microscopy, and television techniques after transplantation of a 0.5-cu mm piece of tumor tissue. The tumor revealed a special microvascular configuration of short, thin-walled, sometimes dilated capillaries running around the edge of the tumor. Large avascular areas appeared in the center part approximately 5 days after tumor transplantation. Although mean capillary blood cell velocity was not different in tumor-containing and tumor-free preparations, localized irregularities of blood flow were observed close to points of endothelial sacculations. Huge platelet conglomerates were consistently noted in capillaries of the tumor, blocking the blood stream temporarily. Due to discrepancies in microvascular morphology and lack of visible vascularization, large parts of this tumor seem to be inaccessible to tumor treatment. This implies that better vascularization of these regions might enhance the efficiency of cancer treatment. The chamber technique, intravital microscopy, and television methods combined with the subsequent, quantitative microvascular analysis may provide a unique means for direct evaluation of local therapy, particularly during early melanoma growth.

Animals↗
PubMed1980

Technical report--a new chamber technique for microvascular studies in unanesthetized hamsters.

An experimental model was designed for direct, quantitative studies of hemodynamic and morphologic parameters in the microcirculation. It consists of implanting a modified Algire chamber in the dorsal skin flap of hamsters and the implementation of two permanent catheters in jugular vein and carotid artery. The microcirculation was studied using intravital microscopy and television techniques for in situ measurements of blood cell velocity and vascular diameters. Due to the poor contrast between blood cells, blood capillaries and surrounding s.c. tissue, microvascular beds were visualized using fluorescent microscopy after i.v. injection of 0.2 ml of 5% FITC-Dextran 150. The combination of optical elements and low amounts of FITC-Dextran improved the contrast of the televised image without changing macro- and micro-hemodynamic parameters, and blood plasma was delineated as bright structure against the substantially darker background of red blood cells and surrounding tissue. This permitted the quantitative study of practically all blood vessels within a given field of s.c. tissue in unanesthetized animals. Blood cell velocity in arterioles was 0.7-1.1 mm/s, 0.2-0.7 mm/s in midcapillaries and reached 0.6 mm/s in collecting venules. Since i.v. injection of drugs and systemic pressure measurements are possible in this model, it provides a unique means for studying the reactivity of the microcirculation over a prolonged period.

Animals↗
PubMed1980

The effect of PEEP ventilation on hemodynamics and regional blood flow with special regard to coronary blood flow.

An experimental study was performed to evaluate the effects of positive end-expiratory pressure (PEEP) on central hemodynamics and on regional blood flow (RBF) using the radioactive microsphere (MS) method. Ten dogs with intact lungs and 10 dogs with oleic acid-induced pulmonary edema were ventilated with PEEP 10 and PEEP 20 (cmH2O). PEEP significantly reduced cardiac output (CO) by 25% at PEEP 10 and 40--50% at PEEP 20 despite volume expansion with dextran 60. RV afterload rose markedly due to a significant increase of pulmonary vascular resistance. PEEP tended to redistribute CO in favor of brain, heart and adrenals, at the expense of stomach, pancreas and thyroid glands. Hepatic artery flow was moderately reduced; renal RBF was seriously affected only when PEEP caused an extreme low-output state. RBF to the RV remained essentially unchanged, whereas RBF to the LV decreased, roughly paralleling the respective ventricular work. Nevertheless, the RV may suffer from underperfusion during PEEP, since its tension-time-index rises; this may indicate increased oxygen needs exceeding actual oxygen delivery.

Adrenal Glands↗
PubMed1980

Incidence, pathomechanism and prevention of dextran-induced anaphylactoid / anaphylactic reactions in man.

The symptoms of dextran-induced anaphylactoid/anaphylactic reactions (DIAR) range from skin reactions to severe circulatory shock (severity grades I-IV). The reported incidence of DIAR varies between 0.03% and 4.7%, severe reactions comprising 0.008% and 0.6% resp. Studies to elucidate the pathomechanism of DIAR and to possibly prevent them were made during the last decade: No evidence for a pathogenic role of contaminating macromolecules was found, but the dextran molecule itself could be incriminated as elicitor agent. High titres of dextran reactive antibodies (DRA) of predominantly IgG class are regularly found in sera of patients with grade III+IV reactions. Such DRA reflect immunization with dextran cross-reactive bacterial polysaccharides or native dextran. No DRA of IgE class were found. Presence of high IgG-DRA levels, reduction of complement factor Clq and histopathological findings in lungs, all indicate that DIAR should be classified as aggregate (immune complex) anaphylaxis. Hapten inhibition was therefore proposed to prevent DIAR. Based on positive results in animal models, clinical trials were started 1978. Hitherto, 60 485 patients have been studied. It is concluded that the combined use of preinjection of 20 ml Dextran 1 (Pharmacia AB, Uppsala, Sweden) and infusion of Macrodex or Rheomacrodex improves the safety of dextran administration.

Anaphylaxis↗